1. Field of the Invention
The present invention relates to a whole blood immunoassay, more particularly a whole blood immunoassay by use of a particle agglutination.
2. Description of Related Art
For immunoassay on infection disease-related test items, serum has been used as a sample to be tested. However, it takes at least about 30 minutes to separate serum from whole blood, including time for blood coagulation and time for subsequent centrifugation.
Typical examples of immunoassay include a radioimmunoassay (RIA), an enzyme immunoassay (EIA), a particle agglutination immunoassay and a counting immunoassay. However, the RIA and the EIA need B(Bound form)/F(Free form) separation after antigen-antibody reaction, and therefore, require time and labor before the results of the assay are obtained.
The particle agglutination immunoassay is advantageous in that it requires only the mixing of a sample to be tested with a suspension of insoluble carrier particles (e.g., latex) sensitized with an antibody or an antigen. It does not require the B/F separation and can be performed by simple operation.
In recent years, however, highly accurate simple immunoassay techniques are demanded. Particularly it has become necessary to judge rapidly whether or not a patient is infected with virus hepatitis, HIV or the like, for example, in the case of emergency operation. Accordingly, it is demanded that assay time from collection of blood up to obtainment of assay results be shortened.
Taking the shortening of the assay time into consideration, it is more desirable to use whole blood collected from a patient than to use serum, as a sample for immunoassay. However, when whole blood is used, the presence of blood cells interferes with the detection of a degree of agglutination of particles.
In view of this, for example, Japanese Unexamined Patent Publication No. HEI 10(1998)-48214 discloses a whole blood assay using a conventional latex agglutination method. According to this disclosure, a whole blood sample is hemolyzed with a surfactant and the resulting sample is tested by a latex turbidimetric immunoassay.
However, this assay has a problem in that the surfactant, which needs to be used in a sufficient concentration for hemolysis, affects the antigen-antibody reaction and a sufficient response cannot be obtained.